The PZT material thickness is measured as what fraction of the sound wavelength?

The PZT material thickness is measured as what fraction of the sound wavelength?

• A. 1/2 wavelength
• B. One-quarter wavelength
• C. Full wavelength
• D. 1/3 wavelength

Answer: (A)

Thickness-mode transducers are designed so that a half-wavelength of the acoustic wave fits across the crystal’s thickness. If the wave in PZT has speed v and the drive frequency is f, the wavelength is lambda = v/f. When t equals lambda/2, the crystal rings in its fundamental thickness mode, giving f = v/(2t). Therefore, the PZT thickness is described as one-half of the sound wavelength. The quarter-wavelength idea you might hear is for the matching layer, not the PZT itself, which is why that option doesn’t describe the PZT thickness.

Thickness-mode transducers are designed so that a half-wavelength of the acoustic wave fits across the crystal’s thickness. If the wave in PZT has speed v and the drive frequency is f, the wavelength is lambda = v/f. When t equals lambda/2, the crystal rings in its fundamental thickness mode, giving f = v/(2t). Therefore, the PZT thickness is described as one-half of the sound wavelength. The quarter-wavelength idea you might hear is for the matching layer, not the PZT itself, which is why that option doesn’t describe the PZT thickness.